91 XP spark problems

[jetski-billy]

i have a 91 xp and it has a spark problem, it will idle all day long if you let it, and it will rev to about 3000-4500 rpm's fine but over that it just surges asthough you are pressing the stop switch every second or so, i took a plug cap off and held the lead to the spark plug, at idle it is fine and when you increase ther revs slowly it is fine but when you get to a certain rev the spark is full on then off,full on then off.you can visiouly see the the spark coming then going and this is exactly when the motor surges, almost as though you are pulling lanyard or something,is there a rev limiter on this machine and could this be the problem? or could it be a faulty CDI unit?
just for the record it does it on both plug leads not just one!
any ideas would be much appreciated

scott

[SP]

The surging sounds more like a lean fuel condition caused by clogged carbs or a seal in the case leaking air in (PTO side).

I started my adventure thinking I had an electrical problem, ended up with a bad crank.

Good luck, pressure test the motor before you start buying anything.....

[jetski-billy]

i have stripped and cleaned the carbs, all looks ok in that department
you can visually see the spark dissapearing then coming back,so on and so on

just tried disconnecting lanyard and stop switch, but still the same

any ideas?

[Bill O'Neal]

Yes in the electrical box is a small black box mounted on a piece of aluminum that is a rev limiter. Sounds like you need another rev limiter.